Task 028: .AMPL File Format

After reviewing the available information, I need to clarify that there is no file format explicitly named ".AMPL" associated with the AMPL (A Mathematical Programming Language) system. AMPL uses files with extensions like .mod (model files), .dat (data files), and .run (script or run files) to define and solve mathematical programming problems. The search results and AMPL documentation do not indicate a distinct ".AMPL" file format. Instead, AMPL files are plain text files with specific syntax for defining models, data, or scripts.

For the purpose of this task, I will assume the user is referring to AMPL's data file format (typically .dat) as the closest match, since it is a core component of AMPL's file system and contains properties intrinsic to its structure. I will define the properties of the .dat file format and implement classes in Python, Java, JavaScript, and C to read, write, and print these properties. If the user intended a different or custom ".AMPL" format, please provide additional details, and I can adjust the response accordingly.

1. Properties of the AMPL Data File Format (.dat)

Based on AMPL documentation, particularly from the AMPL book and related resources, the .dat file format is a plain text format used to specify data for AMPL models. Below are the intrinsic properties of the .dat file format:

• File Extension: .dat
• File Type: Plain text, human-readable, and machine-parsable.
• Structure: Consists of data statements that assign values to sets, parameters, and other model components defined in a corresponding .mod file.
• Syntax:
• Set Declarations: Define sets using the set keyword, e.g., set PRODUCTS := A B C;.
• Parameter Declarations: Assign values to parameters using the param keyword, e.g., param cost := A 10 B 20 C 30;.
• Table Format: Supports tabular data for parameters, e.g., param cost : A B C := 1 10 20 30;.
• Colon-Equal Operator: Uses := to assign values, distinguishing it from standard equality signs.
• Whitespace and Formatting: Flexible whitespace, allowing data to be formatted for readability or compactness.
• Comments: Supports comments starting with # for documentation within the file.
• Character Encoding: Typically ASCII or UTF-8, as it is plain text.
• Delimiter: Uses spaces, tabs, or newlines to separate tokens; commas are optional in some contexts.
• Data Types: Supports numeric values (integers, floats), strings (for set members or symbolic parameters), and indexed collections (e.g., vectors, matrices).
• Portability: Designed to be platform-independent, readable by AMPL solvers on any system.
• File Size: No strict size limit, but performance depends on the solver and system resources.
• Associated Files: Typically paired with a .mod file (model) and optionally a .run file (script) to form a complete AMPL problem instance.

These properties are derived from AMPL’s text file data format as described in the AMPL book (Chapter 9) and related resources.

2. Python Class for AMPL .dat File

Below is a Python class that reads, writes, and prints the properties of an AMPL .dat file. The class parses the file to extract sets and parameters, assuming a basic structure.

import re
import os

class AMPLDataFile:
    def __init__(self, filepath):
        self.filepath = filepath
        self.properties = {
            "extension": ".dat",
            "file_type": "plain text",
            "sets": {},
            "parameters": {},
            "comments": [],
            "encoding": "UTF-8",
            "delimiter": "spaces/tabs/newlines"
        }

    def read(self):
        """Read and decode the .dat file."""
        try:
            with open(self.filepath, 'r', encoding=self.properties["encoding"]) as f:
                content = f.read()
                lines = content.splitlines()

                for line in lines:
                    line = line.strip()
                    if not line or line.startswith('#'):
                        if line.startswith('#'):
                            self.properties["comments"].append(line)
                        continue

                    # Parse set declarations
                    if line.startswith('set'):
                        match = re.match(r'set\s+(\w+)\s*:=\s*([^;]+);', line)
                        if match:
                            set_name, values = match.groups()
                            self.properties["sets"][set_name] = values.split()

                    # Parse parameter declarations
                    elif line.startswith('param'):
                        match = re.match(r'param\s+(\w+)\s*:=\s*([^;]+);', line)
                        if match:
                            param_name, values = match.groups()
                            # Handle simple parameter assignments
                            param_values = {}
                            for pair in values.split():
                                if pair.isalpha():
                                    key = pair
                                    param_values[key] = None
                                elif param_values:
                                    last_key = list(param_values.keys())[-1]
                                    param_values[last_key] = float(pair) if pair.replace('.', '').isdigit() else pair
                            self.properties["parameters"][param_name] = param_values
        except FileNotFoundError:
            print(f"Error: File {self.filepath} not found.")
        except Exception as e:
            print(f"Error reading file: {e}")

    def write(self, output_filepath):
        """Write properties to a new .dat file."""
        try:
            with open(output_filepath, 'w', encoding=self.properties["encoding"]) as f:
                # Write comments
                for comment in self.properties["comments"]:
                    f.write(f"{comment}\n")

                # Write sets
                for set_name, values in self.properties["sets"].items():
                    f.write(f"set {set_name} := {' '.join(values)};\n")

                # Write parameters
                for param_name, values in self.properties["parameters"].items():
                    f.write(f"param {param_name} := ")
                    for key, value in values.items():
                        if value is not None:
                            f.write(f"{key} {value} ")
                        else:
                            f.write(f"{key} ")
                    f.write(";\n")
            print(f"File written to {output_filepath}")
        except Exception as e:
            print(f"Error writing file: {e}")

    def print_properties(self):
        """Print all properties to console."""
        for key, value in self.properties.items():
            print(f"{key}: {value}")

# Example usage
if __name__ == "__main__":
    # Example .dat file content:
    # set PRODUCTS := A B C;
    # param cost := A 10 B 20 C 30;
    # # Sample comment
    dat_file = AMPLDataFile("example.dat")
    dat_file.read()
    dat_file.print_properties()
    dat_file.write("output.dat")

This class:

• Reads a .dat file, parsing sets and parameters using regular expressions.
• Stores properties like extension, file type, sets, parameters, comments, encoding, and delimiter.
• Writes a new .dat file with the parsed data.
• Prints all properties to the console.

3. Java Class for AMPL .dat File

Below is a Java class that performs similar operations.

import java.io.*;
import java.util.*;
import java.util.regex.*;

public class AMPLDataFile {
    private String filepath;
    private Map<String, Object> properties;

    public AMPLDataFile(String filepath) {
        this.filepath = filepath;
        this.properties = new HashMap<>();
        properties.put("extension", ".dat");
        properties.put("file_type", "plain text");
        properties.put("sets", new HashMap<String, List<String>>());
        properties.put("parameters", new HashMap<String, Map<String, String>>());
        properties.put("comments", new ArrayList<String>());
        properties.put("encoding", "UTF-8");
        properties.put("delimiter", "spaces/tabs/newlines");
    }

    public void read() {
        try (BufferedReader reader = new BufferedReader(new FileReader(filepath))) {
            String line;
            Pattern setPattern = Pattern.compile("set\\s+(\\w+)\\s*:=\\s*([^;]+);");
            Pattern paramPattern = Pattern.compile("param\\s+(\\w+)\\s*:=\\s*([^;]+);");

            while ((line = reader.readLine()) != null) {
                line = line.trim();
                if (line.isEmpty() || line.startsWith("#")) {
                    if (line.startsWith("#")) {
                        ((List<String>) properties.get("comments")).add(line);
                    }
                    continue;
                }

                Matcher setMatcher = setPattern.matcher(line);
                if (setMatcher.matches()) {
                    String setName = setMatcher.group(1);
                    String[] values = setMatcher.group(2).trim().split("\\s+");
                    ((Map<String, List<String>>) properties.get("sets")).put(setName, Arrays.asList(values));
                }

                Matcher paramMatcher = paramPattern.matcher(line);
                if (paramMatcher.matches()) {
                    String paramName = paramMatcher.group(1);
                    String[] values = paramMatcher.group(2).trim().split("\\s+");
                    Map<String, String> paramValues = new LinkedHashMap<>();
                    for (int i = 0; i < values.length; i += 2) {
                        if (i + 1 < values.length) {
                            paramValues.put(values[i], values[i + 1]);
                        } else {
                            paramValues.put(values[i], null);
                        }
                    }
                    ((Map<String, Map<String, String>>) properties.get("parameters")).put(paramName, paramValues);
                }
            }
        } catch (IOException e) {
            System.out.println("Error: File " + filepath + " not found or cannot be read.");
        }
    }

    public void write(String outputFilepath) {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFilepath))) {
            // Write comments
            for (String comment : (List<String>) properties.get("comments")) {
                writer.write(comment + "\n");
            }

            // Write sets
            for (Map.Entry<String, List<String>> entry : ((Map<String, List<String>>) properties.get("sets")).entrySet()) {
                writer.write("set " + entry.getKey() + " := " + String.join(" ", entry.getValue()) + ";\n");
            }

            // Write parameters
            for (Map.Entry<String, Map<String, String>> entry : ((Map<String, Map<String, String>>) properties.get("parameters")).entrySet()) {
                writer.write("param " + entry.getKey() + " := ");
                for (Map.Entry<String, String> param : entry.getValue().entrySet()) {
                    writer.write(param.getKey() + " " + (param.getValue() != null ? param.getValue() + " " : ""));
                }
                writer.write(";\n");
            }
            System.out.println("File written to " + outputFilepath);
        } catch (IOException e) {
            System.out.println("Error writing file: " + e.getMessage());
        }
    }

    public void printProperties() {
        for (Map.Entry<String, Object> entry : properties.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }

    public static void main(String[] args) {
        AMPLDataFile datFile = new AMPLDataFile("example.dat");
        datFile.read();
        datFile.printProperties();
        datFile.write("output.dat");
    }
}

This class:

• Uses Pattern and Matcher for parsing sets and parameters.
• Stores properties in a Map and handles file I/O with BufferedReader and BufferedWriter.
• Prints properties and writes a new .dat file.

4. JavaScript Class for AMPL .dat File

Below is a JavaScript class using Node.js for file operations.

const fs = require('fs').promises;

class AMPLDataFile {
    constructor(filepath) {
        this.filepath = filepath;
        this.properties = {
            extension: '.dat',
            file_type: 'plain text',
            sets: {},
            parameters: {},
            comments: [],
            encoding: 'UTF-8',
            delimiter: 'spaces/tabs/newlines'
        };
    }

    async read() {
        try {
            const content = await fs.readFile(this.filepath, this.properties.encoding);
            const lines = content.split('\n');

            for (let line of lines) {
                line = line.trim();
                if (!line || line.startsWith('#')) {
                    if (line.startsWith('#')) {
                        this.properties.comments.push(line);
                    }
                    continue;
                }

                // Parse set declarations
                const setMatch = line.match(/set\s+(\w+)\s*:=\s*([^;]+);/);
                if (setMatch) {
                    const [, setName, values] = setMatch;
                    this.properties.sets[setName] = values.trim().split(/\s+/);
                }

                // Parse parameter declarations
                const paramMatch = line.match(/param\s+(\w+)\s*:=\s*([^;]+);/);
                if (paramMatch) {
                    const [, paramName, values] = paramMatch;
                    const paramValues = {};
                    const tokens = values.trim().split(/\s+/);
                    for (let i = 0; i < tokens.length; i += 2) {
                        if (i + 1 < tokens.length) {
                            paramValues[tokens[i]] = tokens[i + 1];
                        } else {
                            paramValues[tokens[i]] = null;
                        }
                    }
                    this.properties.parameters[paramName] = paramValues;
                }
            }
        } catch (error) {
            console.error(`Error: File ${this.filepath} not found or cannot be read: ${error.message}`);
        }
    }

    async write(outputFilepath) {
        try {
            let output = '';
            // Write comments
            for (const comment of this.properties.comments) {
                output += `${comment}\n`;
            }

            // Write sets
            for (const [setName, values] of Object.entries(this.properties.sets)) {
                output += `set ${setName} := ${values.join(' ')};\n`;
            }

            // Write parameters
            for (const [paramName, values] of Object.entries(this.properties.parameters)) {
                output += `param ${paramName} := `;
                for (const [key, value] of Object.entries(values)) {
                    output += `${key} ${value || ''} `;
                }
                output += ';\n';
            }

            await fs.writeFile(outputFilepath, output, this.properties.encoding);
            console.log(`File written to ${outputFilepath}`);
        } catch (error) {
            console.error(`Error writing file: ${error.message}`);
        }
    }

    printProperties() {
        for (const [key, value] of Object.entries(this.properties)) {
            console.log(`${key}: ${JSON.stringify(value, null, 2)}`);
        }
    }
}

// Example usage
(async () => {
    const datFile = new AMPLDataFile('example.dat');
    await datFile.read();
    datFile.printProperties();
    await datFile.write('output.dat');
})();

This class:

• Uses Node.js fs.promises for asynchronous file operations.
• Parses .dat files with regular expressions and stores properties.
• Writes a new .dat file and prints properties to the console.

5. C Class for AMPL .dat File

C does not have a direct concept of "classes," so I’ll implement a struct with associated functions to mimic class behavior.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <regex.h>

#define MAX_LINE_LENGTH 1024
#define MAX_TOKEN_LENGTH 256

typedef struct {
    char* filepath;
    char* extension;
    char* file_type;
    char* encoding;
    char* delimiter;
    char** comments;
    int comment_count;
    char** set_names;
    char*** set_values;
    int set_count;
    char** param_names;
    char*** param_values;
    int* param_value_counts;
    int param_count;
} AMPLDataFile;

AMPLDataFile* create_ampl_data_file(const char* filepath) {
    AMPLDataFile* data_file = (AMPLDataFile*)malloc(sizeof(AMPLDataFile));
    data_file->filepath = strdup(filepath);
    data_file->extension = ".dat";
    data_file->file_type = "plain text";
    data_file->encoding = "UTF-8";
    data_file->delimiter = "spaces/tabs/newlines";
    data_file->comments = NULL;
    data_file->comment_count = 0;
    data_file->set_names = NULL;
    data_file->set_values = NULL;
    data_file->set_count = 0;
    data_file->param_names = NULL;
    data_file->param_values = NULL;
    data_file->param_value_counts = NULL;
    data_file->param_count = 0;
    return data_file;
}

void read_ampl_data_file(AMPLDataFile* data_file) {
    FILE* file = fopen(data_file->filepath, "r");
    if (!file) {
        printf("Error: File %s not found.\n", data_file->filepath);
        return;
    }

    char line[MAX_LINE_LENGTH];
    regex_t set_regex, param_regex;
    regcomp(&set_regex, "set\\s+(\\w+)\\s*:=\\s*([^;]+);", REG_EXTENDED);
    regcomp(&param_regex, "param\\s+(\\w+)\\s*:=\\s*([^;]+);", REG_EXTENDED);

    while (fgets(line, MAX_LINE_LENGTH, file)) {
        char* trimmed = line;
        while (*trimmed == ' ' || *trimmed == '\t') trimmed++;
        char* end = trimmed + strlen(trimmed) - 1;
        while (end > trimmed && (*end == '\n' || *end == ' ' || *end == '\t')) *end-- = '\0';

        if (!*trimmed || trimmed[0] == '#') {
            if (trimmed[0] == '#') {
                data_file->comments = realloc(data_file->comments, (data_file->comment_count + 1) * sizeof(char*));
                data_file->comments[data_file->comment_count++] = strdup(trimmed);
            }
            continue;
        }

        regmatch_t matches[3];
        if (regexec(&set_regex, trimmed, 3, matches, 0) == 0) {
            data_file->set_names = realloc(data_file->set_names, (data_file->set_count + 1) * sizeof(char*));
            data_file->set_values = realloc(data_file->set_values, (data_file->set_count + 1) * sizeof(char**));
            char* set_name = strndup(trimmed + matches[1].rm_so, matches[1].rm_eo - matches[1].rm_so);
            char* values = strndup(trimmed + matches[2].rm_so, matches[2].rm_eo - matches[2].rm_so);
            data_file->set_names[data_file->set_count] = set_name;

            char** tokens = NULL;
            int token_count = 0;
            char* token = strtok(values, " \t");
            while (token) {
                tokens = realloc(tokens, (token_count + 1) * sizeof(char*));
                tokens[token_count++] = strdup(token);
                token = strtok(NULL, " \t");
            }
            data_file->set_values[data_file->set_count] = tokens;
            data_file->set_count++;
            free(values);
        } else if (regexec(&param_regex, trimmed, 3, matches, 0) == 0) {
            data_file->param_names = realloc(data_file->param_names, (data_file->param_count + 1) * sizeof(char*));
            data_file->param_values = realloc(data_file->param_values, (data_file->param_count + 1) * sizeof(char**));
            data_file->param_value_counts = realloc(data_file->param_value_counts, (data_file->param_count + 1) * sizeof(int));
            char* param_name = strndup(trimmed + matches[1].rm_so, matches[1].rm_eo - matches[1].rm_so);
            char* values = strndup(trimmed + matches[2].rm_so, matches[2].rm_eo - matches[2].rm_so);
            data_file->param_names[data_file->param_count] = param_name;

            char** tokens = NULL;
            int token_count = 0;
            char* token = strtok(values, " \t");
            while (token) {
                tokens = realloc(tokens, (token_count + 1) * sizeof(char*));
                tokens[token_count++] = strdup(token);
                token = strtok(NULL, " \t");
            }
            data_file->param_values[data_file->param_count] = tokens;
            data_file->param_value_counts[data_file->param_count] = token_count;
            data_file->param_count++;
            free(values);
        }
    }

    regfree(&set_regex);
    regfree(&param_regex);
    fclose(file);
}

void write_ampl_data_file(AMPLDataFile* data_file, const char* output_filepath) {
    FILE* file = fopen(output_filepath, "w");
    if (!file) {
        printf("Error writing file: %s\n", output_filepath);
        return;
    }

    for (int i = 0; i < data_file->comment_count; i++) {
        fprintf(file, "%s\n", data_file->comments[i]);
    }

    for (int i = 0; i < data_file->set_count; i++) {
        fprintf(file, "set %s := ", data_file->set_names[i]);
        for (int j = 0; data_file->set_values[i][j]; j++) {
            fprintf(file, "%s ", data_file->set_values[i][j]);
        }
        fprintf(file, ";\n");
    }

    for (int i = 0; i < data_file->param_count; i++) {
        fprintf(file, "param %s := ", data_file->param_names[i]);
        for (int j = 0; j < data_file->param_value_counts[i]; j++) {
            fprintf(file, "%s ", data_file->param_values[i][j]);
        }
        fprintf(file, ";\n");
    }

    fclose(file);
    printf("File written to %s\n", output_filepath);
}

void print_ampl_data_file_properties(AMPLDataFile* data_file) {
    printf("extension: %s\n", data_file->extension);
    printf("file_type: %s\n", data_file->file_type);
    printf("encoding: %s\n", data_file->encoding);
    printf("delimiter: %s\n", data_file->delimiter);
    printf("comments: [");
    for (int i = 0; i < data_file->comment_count; i++) {
        printf("%s%s", data_file->comments[i], i < data_file->comment_count - 1 ? ", " : "");
    }
    printf("]\n");
    printf("sets:\n");
    for (int i = 0; i < data_file->set_count; i++) {
        printf("  %s: [", data_file->set_names[i]);
        for (int j = 0; data_file->set_values[i][j]; j++) {
            printf("%s%s", data_file->set_values[i][j], data_file->set_values[i][j + 1] ? ", " : "");
        }
        printf("]\n");
    }
    printf("parameters:\n");
    for (int i = 0; i < data_file->param_count; i++) {
        printf("  %s: {", data_file->param_names[i]);
        for (int j = 0; j < data_file->param_value_counts[i]; j += 2) {
            printf("%s: %s%s", data_file->param_values[i][j], j + 1 < data_file->param_value_counts[i] ? data_file->param_values[i][j + 1] : "null", j + 2 < data_file->param_value_counts[i] ? ", " : "");
        }
        printf("}\n");
    }
}

void free_ampl_data_file(AMPLDataFile* data_file) {
    free(data_file->filepath);
    for (int i = 0; i < data_file->comment_count; i++) free(data_file->comments[i]);
    free(data_file->comments);
    for (int i = 0; i < data_file->set_count; i++) {
        free(data_file->set_names[i]);
        for (int j = 0; data_file->set_values[i][j]; j++) free(data_file->set_values[i][j]);
        free(data_file->set_values[i]);
    }
    free(data_file->set_names);
    free(data_file->set_values);
    for (int i = 0; i < data_file->param_count; i++) {
        free(data_file->param_names[i]);
        for (int j = 0; j < data_file->param_value_counts[i]; j++) free(data_file->param_values[i][j]);
        free(data_file->param_values[i]);
    }
    free(data_file->param_names);
    free(data_file->param_values);
    free(data_file->param_value_counts);
    free(data_file);
}

int main() {
    AMPLDataFile* dat_file = create_ampl_data_file("example.dat");
    read_ampl_data_file(dat_file);
    print_ampl_data_file_properties(dat_file);
    write_ampl_data_file(dat_file, "output.dat");
    free_ampl_data_file(dat_file);
    return 0;
}

This implementation:

• Uses a struct to store properties and functions to read, write, and print them.
• Employs regex.h for parsing (note: regex support may require linking with -lregex on some systems).
• Manages memory carefully to avoid leaks.
• Reads and writes .dat files and prints properties.

Notes and Assumptions

• Assumption on .AMPL: Since no ".AMPL" file format exists in the AMPL ecosystem, I assumed the user meant AMPL’s .dat file format, as it is the primary data file format. If a custom ".AMPL" format was intended, please provide its specifications.
• Parsing Limitations: The classes handle basic set and parameter declarations. Complex AMPL data structures (e.g., multi-dimensional tables) would require more advanced parsing logic.
• Error Handling: Each implementation includes basic error handling for file operations and parsing.
• Dependencies: The C implementation requires regex support, which may not be standard on all platforms. The JavaScript implementation requires Node.js.
• Testing: The example usage assumes an example.dat file with content like:

set PRODUCTS := A B C;
param cost := A 10 B 20 C 30;
# Sample comment

If you have specific details about a ".AMPL" file format or additional requirements, please clarify, and I can tailor the solution further.